Battery purchase & best shut off location

[acereske]

36 Ford fordor sedan humpback - 6 volt positive ground - I don't get to drive it regularly and it is stored where there is no electricity. I need a battery replacement but have not been able to find the right size (measurement wise) locally. Since I cannot use a battery tender l must install a battery disconnect but don't know where to locate in the car and what type to purchase. Thanking you all in advance for you coming advice. Al